The man believed to be the ringleader of the July 7 bombing attacks appeared last night in a video claiming the killing of 52 people was directly linked to Tony Blair's foreign policy and promising Britain would suffer more suicide attacks.

British-born Mohammad Sidique Khan, from West Yorkshire, said civilians were legitimate targets because of the policies of the UK government, a reference to Iraq and Palestine.

He said: "We are at war and I am a soldier. Now you too will taste the reality of this situation."

The video of the one-time classroom assistant was broadcast by the Arabic news channel al-Jazeera, which followed Khan's video with one of Ayman al-Zawahiri, the second in command of al-Qaida.

Comments from Khan and al-Zawahiri suggest that the terrorist network was more involved in the attacks than western intelligence and analysts had previously thought.

Both tapes seemed to amount to al-Qaida claiming responsibility for the July 7 attacks, and thus potentially more potent than thought after four years of the war on terror.

Prior to the broadcast, counter-terrorism officials had believed the attacks might have been motivated by al-Qaida ideology, but that was the limit of the influence of the network headed by Osama bin Laden.

The tape was produced by the al-Sahab video production house, used by al-Qaida for its earlier propaganda videos.

If the claims are correct then the gap of knowledge of Islamist terrorism among British law enforcement is even bigger than was previously apparent.

Khan, 30, killed himself and six others when he exploded a bomb aboard a train at Edgware Road tube station.

In the video he praised Osama bin Laden and the Iraqi insurgency leader Abu Musab al-Zarqawi as "heroes".

He appeared wearing an olive green jacket, a red and white chequered scarf tied around his forehead, clutching pen and glancing at notes.

His location could not be discerned from the tape, but his brief talk was cogent as he justified the attacks that injured 750 of his fellow citizens, some of whom were maimed and are still in hospital.

Speaking in his Yorkshire accent, he said: "Our words have no impact upon you, therefore I'm going to talk to you in a language that you understand. Our words are dead until we give them life with our blood."

The rhetoric he used was not new, but it was calibrated to touch on sore points about western policy felt by Muslims bitterly opposed to violence.

The bombings of three tube trains and one bus were because the British government continued to commit "atrocities" against Muslims, Khan said.

He said: "Your democratically elected governments continuously perpetuate atrocities against my people and your support of them makes you directly responsible, just as I am directly responsible for protecting and avenging my Muslim brothers and sisters.

"Until we feel security, you will be our target. Until you stop the bombing, gassing, imprisonment and torture of my people, we will not stop this fight."

Warning more indiscriminate violence was to come, Khan, who was married with a young child, said: "I and thousands like me are forsaking everything for what we believe."

In his video, al-Zawahiri, speaking with a gun in the background, said a truce offered by Bin Laden in 2004 had been spurned by western governments and he attacks on London were a result of the "insolence of your governments", according to al-Jazeera's translation.

"I talk to you today about the blessed London battle, which came as a slap to the face of the tyrannical, Crusader British arrogance," al-Zawahiri said. "It's a sip from the glass that the Muslims have been drinking from."

In a warning to all Israelis and countries that joined the international forces in Iraq and Afghanistan, al-Zawahiri said: "The lands and interests of the states that took part in the aggression on Palestine, Iraq and Afghanistan are considered targets for us, so anybody who seeks peace should stay away from these states.

"Blair has brought catastrophes to his people in the middle of the capital, and will bring more, God willing, because he is still fooling his people and insisting and stubbornly treating them like ignorant fools when he keeps repeating that what happened in London has nothing to do with the crimes he has committed in Palestine, Afghanistan and Iraq."

He mocked British Muslims who condemned the attacks. "We tell them treatment in kind is just," he said.

Vowing further attacks, Bin Laden's right-hand man appeared to celebrate making the four British Muslims who committed mass murder against their own citizens of all faiths, vowing al-Qaida will "explode volcanoes" of anger in western countries.

The deputy chief editor of al-Jazeera, Ayman Gaballah, said the Qatar based channel received the tape yesterday by means it would not discuss. The tape was 15 minutes long and contained several clips of fighting in Iraq and the Palestinian territories.